A continuing goal in integrated circuitry fabrication is to form the circuitry components to be smaller and denser over a given area of a semiconductor substrate. One common circuit device is a capacitor, which has a capacitor dielectric region received between a pair of conductive electrodes. In such devices, there is a continuous challenge to maintain sufficiently high storage capacitance despite decreasing area in the denser circuits. Additionally, there is a continuing goal to further decrease cell area. One manner of increasing cell capacitance is through cell structure techniques. Such techniques include three-dimensional cell capacitors, such as trench or stacked capacitors.
Highly integrated memory devices, for example 256 Mbit DRAMs and beyond, are expected to require a very thin dielectric film for the three-dimensional capacitors of cylindrically stacked, trenched or other structures. To meet this requirement, the capacitor dielectric film thickness will be below 2.5 nanometer of SiO2 equivalent thickness. Accordingly, materials other than SiO2 having higher dielectric constants are expected to be used. Si3N4 is one such material which has been used either alone or in combination with silicon dioxide as a capacitor dielectric region. Insulating inorganic metal oxide materials, for example Al2O3, Ta2O5 and barium strontium titanate, have even higher dielectric constants and low leakage currents which make them attractive as capacitor dielectric materials for high density DRAMs, non-volatile memories and other integrated circuitry.
In many of such applications, it will be highly desirable to utilize metal for the capacitor electrodes, thus forming a metal-insulator-metal (MIM) capacitor. In the context of this document, a “metal” encompasses elemental metals, alloys of elemental metals, and metal compounds regardless of stoichiometry. Exemplary conductive metals proposed for use with Al2O3 as the capacitor dielectric material include titanium nitride, tungsten nitride and tantalum nitride. Unfortunately, these materials can be appreciably oxidized when exposed to the typical chemical vapor deposition or atomic layer deposition (ALD) techniques under which Al2O3 (or other dielectric materials) would be deposited. The oxides which form typically have a reduced dielectric constant or increased leakage than Al2O3, thereby having an adverse effect on the capacitor being fabricated. It would be desirable to at least reduce the degree of oxidation of a metal capacitor electrode layer during the formation of an oxide dielectric thereover.
While the invention was motivated from this perspective, it is in no way so limited. The invention is only limited by the accompanying claims, appropriately interpreted in accordance with the doctrine of equivalents, without limiting reference to the specification, and with the specification herein only providing but exemplary preferred embodiments.